Don't turn off the light!

Diabetic retinopathy is thought to be triggered by the high oxygen consumption of retinal rod receptors during dark adaptation, combined with impaired capillary function, but the effect of the light-dark cycle in this process has been unclear. In 29 June The Lancet, Neville Drasdo and colleagues at Cardiff University, UK, shows that night-time illumination could reduce retinal hypoxia and may help prevent the onset of diabetic retinopathy (Lancet 2002, 359:2251-2253).

Drasdo et al. tested the effect of oxygen inhalation on the amplitude of oscillatory potentials (which reflect inner retinal function) in seven patients with type 2 diabetes and eight controls. They observed that the decreased oscillatory potentials induced by dark adaptation in the diabetic patients increased during oxygen inhalation to an amplitude that was comparable to that of the controls before oxygen administration. Oscillatory potentials in the controls were unaffected by oxygen.

"Since light transmission through closed lids is adequate ...